>>>>> Steve Taylor <steve.tay...@aut.ac.nz>
>>>>> on Wed, 24 Jun 2015 00:56:26 +0000 writes:
> Note that objects can have more than one class, in which case your == and
%in% might not work as expected.
> Better to use inherits().
> cheers,
> Steve
Yes indeed, as Steve said, really do!
The use of (class(.) == "....") it is error prone and
against the philosophy of classes (S3 or S4 or ..) in R :
Classes can "extend" other classes or "inherit" from them;
S3 examples in "base R" are
- glm() objects which are "glm"
but also inherit from "lm"
- multivariate time-series are "mts" and "ts"
- The time-date objects POSIXt , POSIXct, POSIXlt
==> do work with inherits(<obj>, <class))
or possibly is( <obj>, <class>)
We've seen this use of
class(.) == ".." (or '!=" or %in% ...)
in too many places; though it may work fine in your test cases,
it is wrong to be used in generality e.g. inside a function you
provide for more general use,
and is best replaced with the use of inherits() / is()
everywhere "out of principle".
Martin Maechler
ETH Zurich
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